Contact lenses made from at least two materials of different flexibility are known in the art. Typical examples have a relatively rigid center portion surrounded by a relatively soft peripheral portion. Such lens offer the combined advantages of hard and soft contact lens: they offer to some degree the visual acuity afforded by rigid contact lenses and the comfort afforded by soft contact lenses.
The composite lenses have several drawbacks. They are difficult to manufacture, they are not durable due to the fact that a junction between the soft and hard portions of the lenses aren't fully joined, and because of the dissimilarity in polymeric materials, changes in ambient conditions can change the shape of the lens.
U.S. Pat. No. 3,488,111 issued to A. A. Isen teaches a hydrophilic hydrogel contact lens with hard central insert. Isen teaches a special design to hold the relatively rigid central portion in the composite lens.
U.S. Pat. No. 3,489,491 issued to Creighton teaches a composite contact lens with a rigid central body portion and a margin of hydrophilic material on the periphery of said central body portion forming the edge of the lens.
U.S. Pat. No. 3,619,044 issued to Kamath teaches a composite lens with a a central zone made of poly(4-methyl pentene-1) and an outer zone or edge made from a softer polymeric material. The lenses are made by placing a rod of the poly(4-methyl pentene-1) in a cylindrical vessel which was then filled with acrylic acid. The acrylic acid was polymerized to form a rod from which buttons were cut and eventually made into composite contact lenses.
U.S. Pat. No. 3,944,347 issued to Barkdoll, et al. discloses a composite contact lens with a hard center and a soft, tough periphery, both portions being formed from fluoropolymers. This composite design is limited to the use of two specific fluoropolymeric materials. The lenses are formed by inserting a central disk of hard fluoropolymer into a sheet of soft fluoropolymer and subjecting the composite to pressure and heat. Thus a distinct junction exists between the two different polymers.
U.S. Pat. No. 3,973,838 issued to Page discloses a design for a composite contact lens with a hard discrete center and a discrete hydrophilic outer portion. U.S. Pat. No. 4,171,878 issued to Kivnev, et al. discloses a similar contact lens with discrete central and peripheral parts.
U.S. Pat. No. 4,093,361 issued to Erickson, et al. teaches a novel composition useful in forming composite contact lenses comprising a mixture of a hydrophilic polymer and a water soluble solid inert substance which can be removed from the mixture by hydration. This mixture is used to form the peripheral portion of a typical contact lens. The material is relatively rigid until the solid inert substance is removed. Therefore, it can be cast with rigid polymeric materials typically used in rigid contact lenses.
U.S. Pat. No. 4,166,255 issued to Graham teaches composite contact lenses and methods for manufacturing the same. One example of the composite lens involves surrounding a rigid optical element with a soft optical material. A second example involves forming a first layer of a soft polymeric material onto the supporting surface of a female mold member, allowing said layer to partially polymerize, applying monomer which cures to form a rigid polymer so as to allow the rigid polymer to diffuse into the soft polymer, and then curing the whole assembly. This would result in a lens with a relatively rigid central portion and a soft peripheral portion.
U.S. Pat. No. 4,208,362 issued to Deichert, et al. teaches a method for making composite contact lenses by partially polymerizing a first material in a concave mold member, adding a second polymerizable material on top of the partially polymerized first material, and completing the polymerization of both materials. This method produces lenses with three regions: one region comprised of a single type of polymeric material, and an intermediate region comprised of a copolymer of the two materials or an alloy of the two materials.
U.S. Pat. No. 4,666,249 issued to Bauman, et al. teaches a method for producing a contact lens with a relatively rigid central portion and a soft skirt. The lens is made by coating a soft lens with a curable material and then selectively curing the coating in the central portion of the lens to form a rigid coating. Ambient temperature change can distort the shape of the lens produced by such means due to differences in coefficients of expansion between the two materials.
U S Pat. No. 4,701,288 issued to Deichert teaches a method for forming a contact lens from at least two dissimilar polymeric materials by placing a monomeric composition in a mold and subjecting part of the monomer to radiation causing the material to polymerize, and then adding a second monomeric material to the periphery of the first partially polymerized material and then curing said composite lens. This method forms a lens with, potentially, a rigid zone, a flexible zone, and an intermediate zone made of the copolymer or alloy of the two monomeric or polymeric materials .